Mathematical Model Of Ultra Large Twin-propeller Twin-rudder Container Ship In Port

With the increasing enlargement of the container ship and relative deterioration of the navigational environment, ship safety has attracted wide attention around the world. Consequently, international demands for ship maneuverability are more rigorous. To meet this requirement, the ultra-large twin-propeller twin-rudder container ship emerges in time and is developing continuously, thus studies on its maneuverability are rightly urgent. In order to improve ship navigational safety, it is necessary to study maneuverability of the ultra-large twin-propeller twin-rudder container ship in-depth, and establish a mathematical model much further, which can simulate maneuvering characteristics of the twin-propeller twin-rudder ship.The thesis has made a further study on the mathematical model of the ultra-large twin-propeller twin-rudder container ship. Based on the modeling mechanism of MMG, a variety of force acting on the hull, propeller and rudder are analyzed firstly, and then the changes of hydrodynamic force and torque caused by different installed positions of the propeller and rudder between twin-propeller twin-rudder ships and single-propeller single-rudder ships are taken into account. Afterwards, the interaction between twin propellers is considered, as well as twin rudders. Then mathematical models of the hull, propeller and rudder are established according to the momentum theorem and angular momentum theorem. The interactions between the hull, propeller and rudder are fully considered, and then advantages and disadvantages of different methods that are utilized to calculate model parameters and hydrodynamic force derivatives are summarized by comparative tests, which are carried out utilizing these methods respectively. The thesis also establishes interference models including low-speed, shallow water, wind and current, which accurately describe the external environmental impact on the ship. Finally the three degrees of freedom (surge, sway, yaw) mathematical model of the twin-propeller twin-rudder ship in port is established to describe the actual motion characteristics of the navigational twin-propeller twin-rudder ship better.The thesis takes the Maersk 3E class container ship "Maersk Marie" as a simulation plant, and then utilizes the S function of Matlab simulation software to establish the ultra-large twin-propeller twin-rudder container ship motion mathematical model. Finally ship tests are carried out through Simulink diagrams. By comparing results of the simulation tests with real ship turning tests, the ship motion mathematical model established in the thesis can accurately reflect maneuverability of the ultra-large twin-propeller twin-rudder container ship. Then according to the established mathematical model, a closed loop gain shaping algorithm and a nonlinear feedback control algorithm are utilized to design controllers for the problem of ship course-keeping. Simulation results show that the control effects of the two kinds of control algorithms are satisfactory, but the nonlinear feedback control algorithm has advantages of energy saving and safety.The ultra-large twin-propeller twin-rudder container ship motion mathematical model established in the thesis can be utilized for the same type ship motion simulation to predict its maneuverability, and it can be utilized to perfect the navigation simulator on the section of ultra-large twin-propeller twin-rudder ship motion mathematical model. Otherwise it can also be utilized to design various control algorithms for ship automatic control problems, such as ship automatic berthing.